Paper drying process and apparatus



May 7, 1935. J. o. WQODSOME 2,000,546

7 PAPER DRYING PROCESS AND APPARATUS Filed April 18, 1931 2 Sheets-Sheet1 y 7, 1935. J. o. woopsoME 2,000,546

PAPER DRYING PROCESS AND APPARATUS Filed April 18, 1951 2 Sheets-Sheet 2Patented May 7, 1935 UNITED STATES PATENT OFFICE 2,000,546 PAPER DRYINGPROCESS AND APPARATUS John 0. Woodsome, Detroit, Mich. Application April18, 1931, Serial No. 531,031 4 Claims. (01. 34-48) This inventionrelates to a paper drying process and apparatus and more particularly toa method of and apparatus for drying paper and other web material withina closed housing by supplying thereto regulated quantities ofconditioned air.

It has heretofore been proposed to enclose the dry end of paper machinesand either to.dry the paper in such enclosed spaces under a substantialvacuum or at least with the exclusion of substantial quantities ofoutside air. It has also been proposed and is common practice to providea hood over the drier section of paper machines with side wallsextending slightly below the level of the top driers, so as to preventthe heated and vapor filled air resulting from the drying operation fromspreading out into the machine room.

The provision of a housing to permit the carrying out of the dryingoperation under substantial vacuum is expensive, since the material ofthe housing must be capable of withstanding the differential pressurebetween the inside and the outside of the housing and must be wellsealed against the admission of air to the interior thereof. Moreover,where the drying operation is carried out under reduced pressure or inthe absence of substantial quantities of air, it is greatly complicateddue to the diificulty of obtaining access to the interior of the housingshould a break of the paper occur or the felt require changing.

Where the paper drying equipment is only partially enclosed, as by ahood with dependent side walls, the heat economy possible through theuse of a vacuum drier cannot be attained but access to the dryingequipment is so much simpler and the construction so much moreinexpensive that this is by far the commoner type of drying apparatusfor paper and like web material.

It is an object of the present invention to provide a completelyenclosed drying apparatus for paper and like web material whereinregulatedquantities of conditioned air are supplied to the interior ofthe drying housing in order to facilitate the drying of the paper andpermit the use of lower drying temperatures than has heretofore beenpossible in the open or semi-enclosed type of drying equipment.

It is a further object of this invention to provide a method of dryingpaper and like web material wherein relatively c001, conditioned air issupplied at points beneath the driers into the in-' terior of a housingenclosing the driers so that the cooled, conditioned air may passupwardly at both the front and rear sides of the drier drums and therebyinduce an outward flow of air and water vapor from the vapor pocketsformed between the drier drums, felt and paper web.

It is a further important object of this invention to provide a novelmethod of and apparatus for drying paper and like web material whereingradual and low temperature dryings may be effected with consequentincreased heat economics and the production of superior quality ofpaper.

Other and further important objects of this invention will be apparentfrom the disclosures in the specification and the accompanying drawings.

This invention (in a preferredform) is illustrated in the drawings andhereinafter more fully described.

On the drawings:

Figure 1 is a side elevational view of drying apparatus embodying theprinciples of my invention, shown more or less diagrammatically.

Figure 2 is an end view of the same with an end wall removed and withparts in section.

Figure 3 is another endview of the same.

As shown on the drawings:

The reference numeral I indicates as a whole a housing for enclosing theusual drier drums 2 of a machinefor making paper or like web mabetweenresilient covered rolls 5 which serve to.

seal the interior of the housing I against the admission of substantialquantities of air along with the paper web. The paper web I then passesunder and over the various drier drums of the drying section and out ofthe housing I between similar resilient covered rolls 6 to a calenderstack I and winder 8.

The housing I and drier drum.2 are mounted upon a flooring 9 that is cutaway underneath the drier drums 2 to provide a continuous passageway Ithe entire length thereof. Said passageway I0 opens directly underneaththe drier drums 2-into the interior of the housing I for the purpose ofsupplying cooled, conditioned air to the interior of the housing, aswill later be more fully explained. The upper part of the space enclosedby the housing I is divided off by horizontal bafiles I I provided withregulating devices I2 to control the rate of flow of -air into the upperspace I3, from which the exhaust gases are drawn through a plurality ofconduits I4 by means of exhaust fans I operated by motors I6.

All of the apparatus for supplying cooled, conditioned air to theinterior of the housing I is suitably positioned upon a flooring I! at alower level than that of the flooring 9. This apparatus comprises ablower I8 having a fresh-air inlet I9 and from which the fresh air isdelivered to an air wash 20, which may be of any standard construction.The washed air is then passed through cooling coils 2| to bring the airbelow its dew point and free it from an excess of water vapor. From thecooling coils 2| the air passes through a coil heater 22, or othersuitable heating device, and thence through an adjustable shuttercontrolled opening 23 into the passageway I0. The bottom wall 24 of thepassageway I is preferably inclined upwardly away from the shuttercontrolled opening 23 to aid in directing the flow of cooled conditionedair up into themterior of the housing I.

The conditioning apparatus is so operated and controlled as to provideair of relatively low humidity at a temperature of about 50 F. Thetemperature and humidity of the entering air will obviously be varied tomeet the requirements of the particular drying operation but in generalthe air will be supplied at a relatively low temperature and humidity inorder that it may have a large capacity for taking up and absorbingwater vapor emanating from the paper being dried.

The capacities of the fans l5 on the exhaust conduits M areintentionally somewhat greater than the capacities of the supply fans l8in order that the flow of air through the interior of the housing I maybe in fairly definite, predetermined paths. The air flows upwardly fromthe passageway l0 and spreads out under the drier drums, since itsupward path is obstructed by the drums themselves and the felt and paperweb passing over the drums, and continues upwardly along both the frontand rear sides of the drier drums, as at A and B, respectively. Avertical bafile 25 extending in spaced relation along the rear side ofthe driers 2 confines the upward flow of air to the restricted space B.This upward flow of air along the front and rear sides of the drierdrums induces an outward flow of heated air and water vapor from thevapor pockets, generally denoted by the letter C formed between thedrums, the felts and paper web's. The tendency is for the heated air andwater vapor from the vapor pockets C to flow outwardly toward both frontand rear sides of the drier section and there be mixed with the upwardflow of cooled conditioned air, which, because of its low temperatureand relative humidity, is capable of absorbing all of the water vaporthus removed from the vapor pockets C. The vapor laden air continues itsupward flow through the dampers or other control devices l2 at the frontside of the drier section and also through spaces 26 provided along therear ends of the drier drums. The exhaust fans l5 continually remove thevapor laden and now heated air from the upper portion of the interior ofthe housing I.

It will be understood that in conjunction with the means and methoddisclosed for supplying cooled conditioned air, the principle of gradualdrying may also be employed by controlling in a manner well known tothose skilled in the art the temperatures of the various drying drums 2in various units or groups to obtaingradient heating. The combination ofthe gradual drying principle with my method of supplying cooled,conditioned air results in much greater uniformity of drying and greatlyincreases the quality of the paper produced. Instead of being dependentupon the outside atmospheric conditions, a drying unit embodying theprinciples of this invention is always supplied with air ofpredetermined temperature and relative humidity so as to be entirelyindependent of the atmospheric conditions. The paper made by my methodis, in general, more uniformly dried across the web and does not suifierfrom over drying at the edges, as is frequently the case on the usualtype of paper machine drier. There is also a less tendency to overdrythe paper or dry it too rapidly. The operating cost of the drier unitsare likewise reduced because of longer life of the drier felts and lesslubrication trouble when drying at lower temperatures.

I am aware that many changes may be made and numerous details ofconstruction may be varied through a wide range without departing fromthe principles of this invention, and I, therefore, do not purposelimiting the patent granted hereon otherwise than necessitated by theprior art.

I claim as my invention:

1. The method of drying a continuous traveling web of paper, whichcomprises passing the paper web over .heated surfaces in an enclosedspace, continuously introducing a stream of relatively cool conditionedair into said enclosed space to travel upwardly at both sides of thetraveling web, therebyinducing an outward flow of heated air and watervapor from the immediate vicinity of said heated web into the upwardlytraveling stream of conditioned air for admixture therewith, andcontinuously withdrawing such admixture.

2. The method of drying a continuous traveling web of paper, whichcomprises subjecting a portion of the paper web to locally applied heatin a confined space from which unregulated supplies of air are excluded,introducing into said confined space at points below the traveling web aregulated supply of relatively cool conditioned air for passage upwardlyon both sides of the traveling web, thereby inducing an outward fiow ofheated air and water vapor from the immediate vicinity of said travelingweb into the conditioned air stream to be admixed therewith and removingthe resulting admixture from said confined space at a point above thetraveling web.

3. In a paper drying apparatus, heated rolls for dryinga travelling webof paper, a housing completely enclosing said heated rolls, said housinghaving openings for the passage of the web therethrough, pressuremeans-about said opening to prevent the ingress of air, vent means inthe top of said housing, a passageway beneath said rolls for introducingair to said housing, pressure means in said passageway for forcing airtherethrough and into said housing, cooling and drying means located insaid passageway and means including baflles for directing the air aboutsaid rolls so as to draw the vapor-laden air from between said rollsinto the air current caused by said pressure means.

4. In a-paper drying apparatus, in combination, a plurality of drierrolls, a housing for completely encasing said rolls, a passagewaybeneath said rolls, means for introducing air through said passageway,and partitions for directing the air from said passageway upwardlyalongside of the rolls to thereby draw heated air from the rolls intothe air current caused by the air introduced through the passageway.

JOHN O. WOODSOME.

